We are using two techniques, radial migration and viscoelastometry, to characterize the DNA of brain cells after treatment with x-rays and drugs. In the radial migration technique, a cell lysate is placed in the annulus of two cylinders, and the center cylinder slowly rotates. DNA in the lysate will migrate towards the center rod, with a velocity proportional to its molecular weight to the 2.5 power. After treatment with x-rays, we expect to see a decrease in the rate of migration due to strand breaks. In the viscoelastic technique, DNA0is again placed in the annulus of two cylinders, and the center cylinder is rotated 50 degrees. The torque is then removed, and the cylinder reverses its direction of rotation under the influence of relaxing DNA. The cylinder's velocity decays with a time constant proportional to the 1.6 power of the molecular weight. Thus after x-rays we would expect to see a decrease in the time constant of the DNA due to strand breaks. On the other hand drug treatments which caused cross linking would increase the retardation time and increase the radial migration rate.